Method for the conversion of conical projections to orthographic projections



2 Sheets-Sheet 1 e .-N\ x/ 1 Jan. 4 1927.

N. H. BROCK METHOD FOR THE CONVERSION OF CONICAL PROJECTIONS TOORTHOGRAPHIC PROJECTIONS Filed June 23, 5 4

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N. H. BROCK METHOD FOR THE CONVERSION OF CONICAL PROJECTIONS TOQRTHOGRAPHIC PROJECTIONS Filed June 23, 1925 2 Sheets-Sheet 7*firm/017.37%?

Patented J an. 4, 1921,

UNITED .STATES' PATENT OFFICE.

Noam'AN H. nnocx, q PHILADELPHIA, PENNSYLVANIA, AssIo n iro nnocx aWEYMOUTH, INconronA'rnn, or PHILADELPHIA, PE NSYLVANIA, A conronA- TIONOF DELAWAR E.

EETHOD FOR THE CONVERSION OF COIfICAL PROJECTIONS TO ORTHOGRAPHIOPROJECTIONS. v

Application filed June as, 1925. Serial No. 38,953.

My invention relates to a method for correctly locating on anorthographica lly prepared traverse of salient points, (including theoptical center-points shown on aerial photographs) the contour lines andpoints showing on the photographic plates, on the scale of the traverseand, generally speaking, my new method consists in projecting acontoured photographic plate on the traverse so that the 0 tical centerof the plate so projected coincides with its location on the traverseand so that a line drawn from the center of the 'plate to asecondselected salient point will coincide with the line con necting the sameoint on the traverse then adjusting the sea e of projection until thesecond salient point on the projection coincides with its locatedposition on the traverse and drawing-the contour line passing throughthis pointand other points adjacent to it, on the traverse and thenchanging the scale of projectiorrof the photograph to correspond withthe known difierence o elevation between the contour line so drawn 'andanother contour line on the plate, and tracing the so located secondcontour line on the traverse.

Where, as is generally the case, an orthographic map is to be preparedfrom a series of overlapping photographic views on ortions of whichcontour lines have ing a traverse of the territory shown in t e seriesof views by known methods, and locating on said traverse pointscorresponding to the optical center points of the contoured plates andone or more other salient points occurring on each plate and thentracing on the traverse the contour lines of each platein the way abovedescribed.

- It is a fact that a photographic view of object points all located inthe same horizontal lane is identical in form with a view 0 the sameobject points in orthographic projections, consequently, the form of acontour line on an orthographic map will be the same as that traced ona'photographic plate. Since, however, the successive contour lines risenearer and nearer to the lens, each higher contour .level will have-been photographed on a larger scale than sary to reduce one. It is thusonly necesl contours to the scale adopted for the datum plane in orderto present each coutour in the correct size and form to fit theorthographic map drawing. 'Methodsby means of which selected pointsoccurring in pairs of photographic views of the ground can be properlylocated in orthographic projections on a traverse constructed from. suchphotographs are well known. It will thus be understood that when'acoutour line containing one of n such points be projected in such ascalethat the photographic image thereof coincides in position with. theplotted location, allother points in the same contour will be projectedin theircorrect orthographic locations and can thenbe traced in on themap tracin in their proper relative positions.

My invention will be best understood as described in connection with thedrawings,

in which: Figures 1 to 4 are perspective views of a series ofphotographic plates taken with f overlapping views,,having say about 60%.overlap so that the center points of each plate show on the adjoiningplates. On

each of these plates the contour lines of the territory lying betweenthe center of the plate and the conjugate center next succeeding plateare trace Figure 5 is a view showing the orthographic map made ontracing cloth from the photographic views by my method.

(point of the Figure 6 is a diagrammatic view illustrating my method ofprojecting the contour lines in corrected scale'on the map drawing,

and

Figure 7 is a diagrammatic side elevation of an apparatus designed forthe convenient practice of my invention by means of an automaticfocusing camera.

A, A, A and A are the photographic plates, on each of which is lndicatedthe center point of the plate indicated at C Q, G and C and the'conjuate center points of the adjoining plates in icated at 0', 0 ,0 and a. BD are salient points showing on plate A their conjugate image points onplate A being indicated at similar points in plate image points onadjoinirag dicated at E F and H are similar B2, D2; E2 F2 r A; theirconjugate plates being in-- points in plate A, their conjugate points,

map prepared from the plates, preferably on tracing cloth. The basis ofthis ma is a traverse prepared from the photograp s by known means, onwhich the center points on each plate spaced by a fixed scale and theline of flight of the aeroplane between the positions in whichsuccessive photographs were taken is correctly indicated, as are also atleast four salient points showing in each view. The method of taking,correcting and contouring plates and of preparing a traverse and maptherefrom is fully described in the Brock and Holst Patent No. 1,565,413of December 15, 1925. See particularly pages 7 and 8 of the printedpatent.

My invention may be considered as animprovement on the method describedin said patent whereby the operation of contouring the map is speededand cheapened.

J Figs. -6 and 7, is a glass tracing table. K is the lens of aprojecting camera. right angle reflector, a prism as shown in M, Fig. 7,is the base of an automatic focusing camera having uprights M whichsupport theglass table top J and a horizontal projectioniM M is avertical slot or guideway. N is a support for the camera having a,horizontal extension N and supporting rollers N 0, O are wedge shapedsupports movable on-the extension M and upon which rest the rollers N Pis a support forthe light box and plate support P supported by rollers Pon the extension N P is the lam Q-is a slide vertically movable in guieway M and having a pivot pin Q} on which is secured a sleeve Q Throu hthis sleeve Q passes a single armed lever R fulcrumed at R, which at itslower end passes through a sleeve S pivotally supported at S to a pointon the support P. T, T indicate the usual light excluding bellows.

The automatic focusing camera indicated in Fig. 7 has been devised foruse in carrying my method into practical use and embodies certain novelfeatures which form the subject matter of an application for LettersPatent filed by Lodewyk J. R. Holst dated June 23, 1925, Serial Number39,002. I p In practicing my invention a series of overlappingphotographic views of the territory to be mapped, preferably reprojectedto make them correspond to views taken with a vertical lens axis and onwhich have been traced contour lines of the territory shown in theviews, are used to prepare a traverse on which are shown the centerpoints of each plate, spaced to the scale of the traverse and connectedby lines which indicate the directionrof flight between each twosuccessive points and on this traverse I also properly locate at leastfour other salient points in each late. The traverse so prepared andprefera ly on tracing cloth is then laid on the glass table top, and aplate A, for example, is placed in the plate sup- Lis a' ort of thecamera and the traverse is adjusted on the table so that the centerpoint of the plate is projected on the same point as located on thetraverse-and so that a line connecting the center point of the platewith the conjugate center 0 of the succeeding plate will correspond withthe line C C of the traverse. I then shift the plates away from ortowards the lens, as it may be necessary to reduce or enlarge the scaleof the contour line'until the projected contour line passing through oneof the salient points of plate A is brought to register with thispoint'as located on the traverse.

This brings the projected image of the contour line to the scale of thetraverse and it can be traced on the traverse as so located. The heightof the selected point being known and the difference in elevation of allthe contour lines being also known, it is a simple matter to readjustthe plate with regard to the lens by distances which will correspond tothe difference in elevation between contour lines and results in eachcontour line being in turn projected on the tracing in the scale of thetracing. Each successive plate is in turn projected on the traversetracing and as a result a correct map is V rapidly, ,produoed.

It is of course necessary that with each scale adjustment of the camerait be re- I focused and the focal plane corresponding to the top of theglass table top must remain fixed for all scale adjustment. This can beeffected in various ways but is very efliciently effected by theprojector constructed as shown in Fig. 7

In this projector when adjusted to project a view on the tracing in thesame scale as that of the plate, the single armed lever should beat anangle of 45 to the vertical, and when it is desired to reduce the scaleof the projected view the wedges O are moved to the left with the effectof lifting the camera support N and all parts supported by it. This ofcourse lifts the lvoted sleeve Q, and turns the lever B. on 1ts fulcrumso that the lower end passing through sleeve S moves the plate to thecorrect distance from the lens, to maintain the focal plane of the imagein the top surface of the traverse-supporting surface.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is: y

1. The method of converting the conical projection of an aerialphotographic view into the orthographic projection of a map whichconsists in preparing a contoured plate of said view and in preparing ageometrically constructed traverse in orthographic projection of two ormore selected points occurring in said contoured view and including theoptical center thereof, projecting' the image of the contoured plate onthe points adjacent thereto,

traverse drawin by means of a suitable projecting camera, ringing theprojected optical center in coincidence with the plotted, positionthereof on the drawing, ad usting the drawing with reference to theprojected view until a line connecting the center and a selected pointas projected coincides in direction with the dlrection between thecorresponding points as plotted on the traverse; changing the scale ofthe projection until the selected point as projected coincides inlocation with the plotted location thereof; drawing on the traverse thecontour line passing through this selected point and then changing thescale of the projection in conformity with the known difference inelevation between the contour line so drawn and the contour line next tobe drawn, repeating the scale of adjustments of the projectionsuccessively for each contour line and drawing these when so adjusted,until completion of the orthographic drawing of said view.

2. The method of claim 1 as applied to the making of a composite map inorthographic projecting each projection of the aggregate area includedin a continuous series of photographic views taken so as to constitute aseries of overlapping pairs of plates on each of which is shown theconjugate center point of the other member of the pair and on one plateof each such pair are traced the contour lines of the section lyingbetween its center and the conjugate center of the other plate of thepair, characterized by producingxby geometric construction a traverse inort ographic projection of selected points occurring on said-contouredlates including the. optical center of each p ate of the series, thensuccessively contoured plate on the traverse and drawing thereof thecontour lines as set out in claim 1, and aligning each successivecontoured plate in relation to the previously traced drawing of thepreceding view so that the projected direction of the line uniting theoptical center of the successive view with that of the precedin view Iwill coincide with the plotted direction of this line as shown on, thetraverse.

NORMAN H. BROCK.

